Note: Descriptions are shown in the official language in which they were submitted.
CA 02467903 2004-05-20
SELF SEALING EXPANDABLE INFLATABLE PACKERS
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] Aspects of the present relate to a sealing apparatus. Particularly, the
present invention relates to an expandable sealing apparatus. More
particularly,
the present invention relates to an expandable sealing apparatus for isolating
sections of a wellbore.
Description of the Related Art
[00021 In the oil and gas exploration and production industry, boreholes are
drilled through rock formations to gain access to hydrocarbon-bearing
formations,
to allow the hydrocarbons to be recovered to surface. During drilling of a
typical
borehole, which may be several thousand feet in length, many different rock
formations are encountered.
[0003] Rock formations having problematic physical characteristics, such as
high permeability, may be encountered during the drilling operation. These
formations may cause various problems such as allowing unwanted water or gases
to enter the borehole; crossflow between high and low pressure zones; and
fluid
communication between a highly permeable formation and adjacent formations. In
instances where a sub-normal or over-pressured formation is sealed off, the
permeability of the formation may be such that high pressure fluids permeate
upwardly or downwardly, thereby re-entering the borehole at a different
location.
[0004] Damage to rock formations during drilling of a borehole may also cause
problems for the drilling operation. Damage to the formation may be caused by
the
pressurized drilling fluid used in the drilling operation. In these
situations, drilling
fluid may be lost into the formation. Loss of drilling fluid may cause the
drilling
operation to be halted in order to take remedial action to stabilize the rock
formation. Loss of drilling fluid is undesirable because drilling fluids are
typically
expensive. In many cases, drilling fluids are re-circulated and cleaned for
use in
CA 02467903 2004-05-20
subsequent drilling procedures in order to save costs. Therefore, loss of high
quantities of drilling fluid is unacceptable.
[0005] One method of overcoming these problems involves lining the borehole
with a casing. This generally requires suspending the casing from the wellhead
and cementing the casing in place, thereby sealing off and isolating the
damaged
formation. However, running and cementing additional casing strings is a time-
consuming and expensive operation.
[0006] Furthermore, due to the installation of the casing, the borehole
drilled
below the casing has a smaller diameter than the sections above it. As the
borehole continues to be extended and casing strings added, the inner diameter
of
the borehole continues to decrease. Because drilling operations are carefully
planned, problematic formations unexpectedly encountered may cause the inner
diameter of the borehole to be overly restricted when additional casing
strings are
installed. Although this may be accounted for during planning, it is generally
undesired and several such occurrences may cause a reduction in final bore
diameter, thereby affecting the future production of hydrocarbons from the
well.
[0007] Alternatively, inflatable packers may be used to seal off a portion of
a
wellbore. Typically, the inflatable packer utilizes an inflatable elastomeric
bladder
to create a fluid seal within the surrounding wellbore or casing. The bladder
may
be inflated by injecting fluid under pressure into the bladder. In this
manner, the
bladder is inflated into contact with the wellbore. Typically, the pressure in
the
bladder is increased to greater than that of the pore pressure of the
formation. In
this respect, a net seal load is created, thereby sealing off the wellbore.
[0008] While the inflatable packer is a viable method of sealing a wellbore,
there
are potential problems associated with its application.. For example, the
actuation
of the inflatable packer is operated through a complex valve system that may
not
function properly. Also, like the casing strings, the inflatable packer
reduces the
inner diameter of the wellbore, thereby potentially limiting the production
capacity of
the wellbore.
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[0009] More recently, expandable tubular technology has been developed to
install casing strings without significantly decreasing the inner diameter of
the
wellbore. Generally, expandable technology enables a smaller diameter tubular
to
pass through a larger diameter tubular, and thereafter be expanded to a larger
diameter. In this respect, expandable technology permits the formation of a
tubular
string having a substantially constant inner diameter, otherwise known as a
monobore. Accordingly, monobore wells have a substantially uniform through-
bore
from the surface casing to the production zones.
[0010] A monobore well features each progressive borehole section being cased
without a reduction of casing size. The monobore well offers the advantage of
being able to start with a much smaller surface casing but still end up with a
desired
size of production casing. Further, the monobore well provides a more
economical
and efficient way of completing a well. Because top-hole sizes are reduced,
less
drilling fluid is required and fewer cuttings are created for cleanup and
disposal.
Also, a smaller surface casing size simplifies the wellhead design as well as
the
blow out protectors and risers. Additionally, running expandable liners
instead of
long casing strings will result in valuable time savings.
[0011] Expandable tubular technology has recently been applied to cased hole
packers. It has been discovered that expandable packers can be expanded in
situ
so as to enlarge the inner diameter. This, in turn, enlarges the path through
which
both fluid and downhole tools may travel. Expandable packers are expanded
through the use of a cone-shaped mandrel or by an expansion tool with
expandable, fluid actuated members disposed on a body and run into the
wellbore
on a tubular string. During the expansion operation, the walls of the
expandable
packer are expanded past their elastic limit. The expandable packer may be
expanded against an existing casing to hang a string of casing or seal off an
annular area. Consequently, expandable packers allow for the use of larger
diameter production tubing, because the conventional slip mechanism and
sealing
mechanism are eliminated.
[0012] An expandable packer is typically run into the wellbore with a running
assembly disposed at an end of a drill string. The running assembly generally
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includes an expansion tool, a swivel, and a running tool. The expansion tool
is
disposed at the bottom end of the drill string. Next, the swivel is disposed
between
the expansion tool and the running tool to allow the expansion tool to rotate
while
the running tool remains stationary. Finally, the running tool is located
below the
swivel, at the bottom end of the running assembly. The running tool is
mechanically attached to the expandable packer through a mechanical holding
device.
[0013} After the expandable packer is lowered to a predetermined point in the
well, the expandable packer is ready to be expanded into contact with the
wellbore
or casing. Subsequently, the expansion tool is activated when a hydraulic
isolation
device, like a ball, is circulated down into a seat in the expansion tool.
Thereafter,
fluid is pumped from the surface of the wellbore down the drill string into
the
expansion tool. When the fluid pressure builds up to a predetermined level,
the
expansion tool is activated, thereby starting the expansion operation. During
the
expansion operation, the swivel allows the expansion tool to rotate while the
packer
and the running tool remain stationary. After the expandable packer has been
expanded against the wellbore or casing, the running assembly is deactivated
and
removed from the well.
[0014] While expanding tubulars in a wellbore offer obvious advantages, there
are problems associated with using the technology to create a packer through
the
expansion of one tubular into a wellbore or another tubular. For example, an
expanded packer with no gripping structure on the outer surface has a reduced
capacity to support the weight of the entire packer. This is due to a reduced
coefficient of friction on the outer surface of the expandable packer. Also,
the
expandable packer may not expand sufficiently to contact the wellbore and form
a
seal therewith. More importantly, the expansion of the expandable packer in an
open-hole wellbore may result in an ineffective seal between the expanded
packer
and the surrounding wellbore.
[0015] There is a need, therefore, for a packer that will create an effective
seal
by exerting pressure against a cased wellbore or an open-hole wellbore. There
is a
further need for a packer that will not reduce the diameter of the wellbore.
There is
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yet a further need for a packer that will expand sufficiently to form a seal
with the
wellbore.
SUMMARY OF THE INVENTION
[0016] The present invention generally relates to a sealing apparatus for
isolating a wellbore. In one aspect, the present invention provides an
expandable
sealing apparatus having an expandable tubular and a sealing element disposed
around the tubular. A chamber for maintaining a fluid is defined between the
sealing element and the tubular. The sealing apparatus also includes a self-
isolating layer disposed in the chamber, wherein the self-isolating layer is
adapted
and arranged to regulate fluid flow through the chamber. Fluid supplied to the
chamber may inflate the sealing element, thereby urging the sealing element
into
contact with the wellbore. The pressure in the chamber causes the self-
isolating
layer to close off, thereby retaining the pressure in the chamber.
[0017] In another aspect, the present invention provides a method for
isolating a
wellbore. The method includes running a sealing apparatus into the wellbore.
The
sealing apparatus having a tubular body; a sealing element disposed around the
tubular body; and a self-isolating layer disposed between the tubular body and
the
sealing element. The method further includes expanding the sealing apparatus
and
inflating the sealing element. Preferably, the pressure in the inflated
sealing
element is greater than the pore pressure of the formation.
[0018] In another embodiment, the method may also include supplying fluid into
a chamber defined by the tubular body and the sealing element to expand the
sealing apparatus. The fluid may be regulated to create a pressure
differential
between the chamber and the tubular body. The pressure differential causes the
self-isolating screen to close, thereby retaining the pressure necessary to
inflate the
sealing element.
[0019] In another aspect still, the present invention provides a seal
assembly.
The seal assembly includes an expandable tubular and a sealing member disposed
at each end of the tubular. The sealing members may straddle a section of the
wellbore to isolate that section from other sections of the wellbore.
CA 02467903 2011-07-12
[0019a] In an aspect of the invention there is provided an expandable sealing
apparatus, comprising an expandable tubular; a sealing element disposed around
the tubular, a chamber defined between the sealing element and the tubular
wherein the chamber is in selective fluid communication with the expandable
tubular and a self-isolating layer disposed in the chamber. The self-isolating
layer
is adapted and arranged to regulate fluid flow into the chamber.
[0019b] In another aspect of the invention there is provided a method for
isolating
a wellbore. The method comprises the steps of running a sealing apparatus into
the
wellbore. The sealing apparatus has a tubular body; one or more sealing
elements
disposed around the tubular body and a self-isolating layer disposed between
the
tubular body and the one or more sealing elements. The sealing apparatus is
expanded and fluid is supplied into a chamber defined between the tubular body
and the one or more sealing elements to inflate the sealing apparatus. The one
or
more sealing elements are inflated. A pressure differential is created between
the
chamber and a bore of the tubular body and the self-isolating layer is closed
to
retain the pressure in the chamber.
[0019c] In another aspect of the invention there is provided a seal assembly
comprising an expandable tubular and a first sealing member disposed at a
first
end of the tubular. A second sealing member is disposed at a second end of the
tubular, wherein each of the first and second sealing members includes an
expandable mandrel, a sealing element disposed around the mandrel and the
chamber defined between the sealing element and the mandrel and in fluid
communication with the mandrel. A self-isolating layer disposed in the
chamber,
wherein the self-isolating layer is adapted and arranged to regulate fluid
flow into
the chamber and is actuatable by a fluid pressure in the chamber to close off
fluid
flow into the chamber.
[0019d] In another aspect of the invention there is provided an expandable
sealing apparatus comprising an expandable tubular, a sealing element disposed
around the tubular and a chamber defined between the sealing element and the
tubular. There is a pressure-isolating layer disposed in the chamber, wherein
the
5a
CA 02467903 2011-07-12
pressure-isolating layer is adapted to regulate fluid flow into the chamber. A
permeable membrane is disposed between a mandrel and the pressure-isolating
layer.
[0019e] In another aspect of the invention there is provided a seal assembly
comprising an expandable tubular, a sealing member disposed around the tubular
and a pressure isolating mechanism adapted to seal off fluid communication
between the expandable tubular and the sealing member when a pressure
differential is created between the expandable tubular and the sealing member.
[0019f] In another aspect of the invention there is provided a method for
isolating
a wellbore. The method comprises running a sealing apparatus into the
wellbore.
The sealing apparatus has a tubular body and one or more sealing elements
disposed around the tubular body. The sealing apparatus is expanded, the one
or
more sealing elements inflated and a pressure differential is initiated
between the
tubular body and the one or more sealing elements. Fluid communication between
the tubular body and the one or more sealing elements is closed off.
5b
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BRIEF DESCRIPTION OF THE DRAWINGS
[0020} So that the manner in which the above recited features of the present
invention, and other features contemplated and claimed herein, are attained
and
can be understood in detail, a more particular description of the invention,
briefly
summarized above, may be had by reference to the embodiments thereof which
are illustrated in the appended drawings. It is to be noted, however, that the
appended drawings illustrate only typical embodiments of this invention and
are
therefore not to be considered limiting of its scope, for the invention may
admit to
other equally effective embodiments.
[0021] Figure 1 is a schematic cross-sectional view of a partially completed
wellbore.
[0022] Figure 2 is a schematic view of a seal assembly according to aspects of
the present invention disposed in the wellbore of Figure 1. The seal assembly
is
shown in the unexpanded configuration.
[0023] Figure 3 is a partial cross-sectional view of one embodiment of the
sealing member of the present invention. The sealing member is shown in the
unactuated configuration.
[0024] Figure 4 is a schematic view of the seal assembly of Figure 2 in the
expanded, uninflated configuration.
[0025] Figure 5 is a partial cross-sectional view of the sealing member of
Figure
3 during inflation.
[0026] Figure 6 is a schematic view of the seal assembly of Figure 2 in the
expanded, inflated configuration.
[0027] Figure 7 is a partial cross-sectional view of the sealing member of
Figure
3 in the actuated configuration.
[0028] Figure 8 is a partial cross-sectional view of another embodiment of the
sealing member of the present invention. The sealing member is shown in the
unactuated configuration.
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[0029] Figure 9 is a partial cross-sectional view of the sealing member of
Figure
8 during inflation.
[0030] Figure 10 is a partial cross-sectional view of the sealing member of
Figure 8 in the actuated configuration.
[0031] Figure 11 is a partial cross-sectional view of another embodiment of
the
sealing member of the present invention. The sealing member is shown in the
unactuated configuration.
[0032] Figure 12 is a schematic view of another embodiment. of the seal
assembly of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0033] Figure 1 is a schematic illustration of a partially completed wellbore
10.
The wellbore 10 is initially drilled to a first depth 12 and may be logged to
determine
certain geological characteristics of the rock formations in the region of the
wellbore
10. As shown, a casing 14 has been installed in an upper portion 18 of the
wellbore 10 and cemented 16 into place. Thereafter, the wellbore 10 is
extended
by drilling a smaller diameter wellbore section 20 below the casing 14 through
a
number of rock formations illustrated at 22-26.
[0034] In this example, during drilling of the wellbore section 20, the rock
formation 24 was unexpectedly found to be highly permeable, and drilling fluid
has
been lost into the formation 24. Loss of drilling fluid may be detected by a
loss of
circulation and a drop in the pit volume of drilling fluid. As a result,
drilling
operations have been suspended.
[0035] To prevent further loss of drilling fluid into the formation 24 and
continue
well completion operations, a seal assembly 50 according to aspects of the
present
invention is located in the wellbore 10 as illustrated in Figure 2. The seal
assembly
50 includes a first sealing member 100A and a second sealing member 100B
disposed at each end of an expandable tubular 110. In this embodiment, each of
the sealing members 100A, 100B are similarly constructed. It is understood
that
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the expandable tubular 110 may include one or more tubulars connected
together.
Additionally, the expandable tubular 110 may include any suitable expandable
tubular for wellbore operations, including expandable solid tubulars,
expandable
slotted tubulars, and expandable screens.
[0036] Initially, the wellbore 10 is underreamed to form a larger bore
diameter 42
before the seal assembly 50 is installed as illustrated in Figure 2.
Thereafter, the
seal assembly 50 is located in the wellbore 10 to isolate the rock formation
24.
Specifically, the seal assembly 50 is positioned such that the sealing members
100A, 100B straddle the formation 24 to be blocked off. The seal assembly 50
is
run into the wellbore 10 on an upper string of expandable solid tubular 48
adapted
and arranged to locate the seal assembly 50 in the underreamed section 42. The
upper string 48 is suspended from the casing 14 by an expandable liner packer
49.
A lower string of tubular 51 may be attached below the seal assembly 50 to
facilitate other operations downhole.
[00371 Figure 3 depicts a sectional view of a sealing member 100 suitable for
use with the seal assembly 50 according to aspects of the present invention.
The
sealing member 100 includes an expandable mandrel 115 and an inflatable
sealing
element 120 mounted on the mandrel 115. The sealing element 120 may be made
from any suitable expandable material, including an elastomeric material such
as a
swelling elastomer or a rubber material such as natural rubber. A chamber 125
is
defined between the sealing element 120 and the mandrel 115. One or more ports
117 may be formed in the mandrel 115 to provide fluid communication between
the
bore 118 of the mandrel 115 and the chamber 125. Fluid supplied to the chamber
125 may serve to inflate the sealing element 120. A. series of reinforcing
ribs 127
are disposed at each end of the sealing element 120 to provide support for the
sealing element 120 after inflation. The ribs 127 may be made of metal,
composite,
carbon-fiber or other suitable material as is known to a person of ordinary
skill in
the art. Figure 3 depicts the sealing member 100 in the run-in uninflated
position.
[0038] In one aspect, the sealing member 100 may include a self-isolating
mechanism to maintain the sealing element 120 in an inflated state. In one
embodiment, a permeable membrane 130 may be disposed between the mandrel
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CA 02467903 2004-05-20
115 and the sealing element 120. The membrane 130 may be made of Teflon or
an elastomeric material such as rubber. The permeable membrane 130 may
include one or more openings 135 for fluid communication.
[0039] A self-isolating screen 140 may be disposed around the permeable
membrane 130. The self-isolating screen 140 is adapted and arranged to
maintain
the pressure in the chamber 125 after the sealing element 120 is inflated. The
screen 140 includes one or more apertures 142 for fluid communication. Each of
the apertures 142 is provided with a flow control member 143 to regulate the
flow of
fluid therethrough. An exemplary flow control member 143 includes a flap 143
connected to the screen 140 at one end and unsecured at another end as shown
in
Figure 3. Preferably, the flap 143 is located interior to the chamber 125 and
is of
sufficient size to cover or close off the respective aperture 142. The flaps
143 are
actuatable by a pressure differential between the bore 118 and the chamber
125.
During inflation, the flap 143 may be caused to flex away from aperture 142 to
allow
fluid to flow into the chamber 125, thereby inflating the sealing element 120.
Conversely, the flap 143 may flex toward the aperture 142 to seal off the
chamber
125, thereby isolating the pressure in the chamber 125. In one embodiment,
self-
isolating screen 140 may be made of metal. In another embodiment, a sealing
material may be disposed around the perimeter of the flap 143 to facilitate
closure
of the aperture 142.
[0040] In operation, the seal assembly 50 is formed by connecting a sealing
member 100A, 100B at each end of an expandable tubular 110. The seal
assembly 50 is disposed in the welibore as shown in Figure 2. Thereafter, an
expander tool is employed to expand the seal assembly 50. Expansion of the
seal
assembly 50 brings the sealing members 100A, 100B closer to the wall 42 of the
wellbore (or into contact with the wall 42), as illustrated in Figure 4.
Particularly, the
expandable mandrels 115 are expanded to a greater internal diameter, thereby
causing a corresponding expansion of the sealing elements 100A, 100B. It is
understood that the sealing elements 100A, 100B may be expanded into contact
with the welibore wall without deviating from the aspects of the present
invention.
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[0041] Any suitable expander tool known to a person of ordinary skill in the
art
may be utilized to expand the seal assembly 50. An exemplary expander tool is
disclosed in Simpson, U.S. Patent No. 6,457,532, issued on October 1, 2002,
which patent is herein incorporated by reference in its entirety. In one
embodiment,
the expander tool may include a rotary expander tooll acting outwardly against
the
inside surface of the seal assembly 50. The expander tool has a body, which is
hollow and generally tubular with connectors and for connection to other
components of a downhole assembly. The connectors are of a reduced diameter
compared to the outside diameter of the longitudinally central body part of
the
expander tool. The central body part of the expander tool has three recesses,
each
holding a respective roller. Each of the mutually identical rollers is
somewhat
cylindrical and barreled. Each of the rollers is mounted by means of an axle
at
each end of the respective roller and the axles are mounted in slidable
pistons.
The rollers are arranged for rotation about a respective rotational axis that
is
parallel to the longitudinal axis of the expander tool and radially offset
therefrom at
120-degree mutual circumferential separations around the central body. The
pistons are sealed within each recess and are radially extendable therein. The
inner end of each piston is exposed to the pressure of fluid within the core
of the
tool by way of the radial perforations in the core. In this manner,
pressurized fluid
provided from the surface of the well, can actuate the pistons and cause them
to
extend outward whereby the rollers contact the inner wall of the seal assembly
50
to be expanded. Other exemplary expander tools include a cone-shaped mandrel
that can be axially traversed to expand the seal assembly 50. The expander
tool is
retrieved at the completion of the expansion.
[00421 The sealing members 100A, 100B may now be inflated to seal off the
wellbore 10. A fluid from the surface is supplied to the chambers 125 of the
sealing
members 100A, 100B to inflate the sealing elements 120. Preferably, the fluid
is
inert to the well and drilling fluids. An inflation tool may be used to supply
the fluid
under pressure to the chambers 125. The fluid is initially forced through the
ports
117 of the mandrel 115 and then through the openings 135 of the permeable
membrane 130. Thereafter, the fluid flow past the apertures 142 of the self-
isolating screen 140 and exit into the chamber 125, thereby inflating the
chamber
CA 02467903 2004-05-20
125. Figure 5 illustrates the seal 100 during the inflation process. As shown,
the
pressurized fluid causes the flap 143 to flex away from the. aperture 142,
thereby
opening the aperture 142 for fluid communication. Consequently, the sealing
element 120 is expanded into contact with the wellbore 10. In this respect, a
large
pressure energized seal load is generated between the sealing member 100 and
the wellbore 10 to provide the desired zone isolation.
[0043] After the sealing members 100A, 1008 have been sufficiently inflated,
the
pressurized fluid is released. Figure 6 illustrates the seal assembly 50 after
inflation. As a result, a pressure differential is created between the chamber
125
and the bore 118 of the mandrel 115. Particularly, the chamber 125 has a
higher
pressure than the hydrostatic pressure in the mandrel 115. As the fluid in the
chamber 125 tries to equalize the pressures by flowing out of the chamber 125
toward the mandrel 115, the self-isolating screen 140 closes off and the
pressure in
the chamber 125 is applied against the permeable membrane 130, as illustrated
in
Figure 7. Particularly, the pressurized fluid causes the flap 143 to flex
toward the
aperture 142, thereby closing off the aperture 142 for fluid communication.
Moreover, the pressure in the chamber 125 causes the screen 140 to press
against
the membrane 130 to further close off the apertures 142. In this respect, the
pressure is trapped in the chamber 125 to maintain the energized seal load. In
this
manner, the seal assembly 50 may be actuated to provide zone isolation.
[0044] In another aspect, an isolation plug 160 may be inserted into the ports
117 of the mandrel 115 prior to run-in, as illustrated in Figure 3. The
isolation plugs
160 may prevent premature inflation of the sealing element 127. Preferably,
the
isolation plugs 160 include a hollow interior. During expansion, the expander
tool
may break the isolation plugs 160, thereby opening the ports 117 for fluid
communication. In this manner, the seals 100 may be adapted to prevent
premature inflation.
[0045] Figure 8 illustrates another embodiment of a sealing member 800
suitable for use with the seal assembly 50 according to aspects of the present
invention. The sealing member 800 includes an expandable mandrel 815 and an
inflatable sealing element 820 mounted on the mandrel 815. The sealing element
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820 may be made from any suitable expandable material, including an
elastomeric
material such as a swelling elastomer or a rubber material such as natural
rubber.
A chamber 825 is defined between the sealing element 820 and the mandrel 815.
One or more ports 817 may be formed in the mandrel 815 to provide fluid
communication between the bore 818 of the mandrel 815 and the chamber 825.
Fluid supplied to the chamber 825 may serve to inflate the sealing element
820. A
series of reinforcing ribs 827 are disposed at each end of the sealing element
820
to provide support for the sealing element 820 after inflation. Figure 8 shows
the
sealing member 800 in the run-in uninflated position.
[0046] The sealing member 800 is provided with a self-isolating layer 840
disposed around mandrel 815. The self-isolating layer 840 includes a series of
flow
control members 843 to regulate the flow of fluid through the ports 817. An
exemplary flow control member 843 includes a flap 843 secured at one end to
the
mandrel and unsecured at another end, as shown in Figure 8. The series of
flaps
843 are located interior to the chamber 825 and are adapted and arranged to
block
off fluid communication through the ports 817. In one embodiment, the secured
ends of adjacent flaps 843, 843A straddle a port 817. The free end of each
flap
843 contacts or lies against a secured end of the adjacent flap 843A.
Preferably,
the flaps 843, 843A .overlap sufficiently such that the adjacent flaps 843,
843A
remain in contact after expansion. The free end may be covered or impregnated
with a sealing material 850 that allows a seal to be formed between the
adjacent
flaps 843, 843A. The flaps 843 are actuatable by a pressure differential
between
the bore 818 and the chamber 825. During inflation, the flap 843 may flex away
from port 817 to allow fluid to flow into the chamber 825, thereby inflating
the
sealing element 820. Conversely, when the pressure in the bore 818 is
released,
the flap 843 may bend toward the port 817 to seal off the chamber 825, thereby
isolating the pressure in the chamber 825.
[0047] In operation, the seal assembly .50 is initially expanded to a greater
diameter. As shown, the seal assembly 50 is expanded against a casing 805 in a
wellbore 10. Thereafter, the sealing members 800 are inflated to seal off the
wellbore 10. A fluid from the surface is supplied to the chambers 825 of the
sealing
members 800 to inflate the sealing elements 820. The fluid is initially forced
12
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through the ports 817 of the mandrel 815 and flows past the flaps 843 in the
chamber 825, as illustrated in Figure 9. As shown, the pressurized fluid
causes the
flap 843 to flex away from the adjacent flap 843A, thereby opening the port
817 for
fluid communication. Pressurized fluid in the chamber 825 expands. the sealing
element 820 into contact with the wellbore 10. In this respect, a large
pressure
energized seal load is generated between the sealing member 820 and the
wellbore 10 to provide the desired zone isolation.
[0048] After the sealing members 800 have been sufficiently inflated, the
pressurized fluid is released. Figure 10 shows the sealing member 800 after
inflation. As a result, a pressure differential is created between the chamber
825
and the bore 818 of the mandrel 815. Particularly, the chamber 825 has a
higher
pressure than the hydrostatic pressure in the mandrel 815. As the fluid in the
chamber 825 tries to equalize the pressures by flowing out of the chamber 825
toward the bore 818, the pressurized fluid causes the unsecured end of the
flap
843 to contact the adjacent flap 843, thereby closing off the port 817 for
fluid
communication. In this respect, the self-isolating layer 840 traps the
pressure in the
chamber 825 to maintain the energized seal load. In this manner, the seal
assembly 50 may be actuated to provide zone isolation.
[0049] Although the flow control members 143, 843 in the above embodiments are
arranged axially along the mandrel 115, 815, it is understood that the flow
control
members may also be arranged radially around the mandrel as illustrated in
Figure
11. Figure 11 shows a cross-sectional view of an embodiment of the sealing
member 900 in which the flow control members 943 are arranged radially around
the mandrel 915. The series of flow control members 943 overlap each other to
regulate fluid flow through the ports 917 in the mandrel 915.
[0050 In another aspect, a solid granular filler material may be provided in
the
chamber. An exemplary filler material may include a mixture of bentonite
(absorbent aluminum silicate clay) and a dry, powdered water soluble polymer
such
as polyacrylamide, as disclosed in U.S. Patent No. 3,909,421. The filler
material
may react with the fluid supplied to the chamber to form a viscous fluid-solid
mixture that cannot pass through the self-isolating screen. Additionally, the
filler
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material increases in size as it absorbs fluid. Accordingly, the applied
pressure
may be relaxed once the sealing member has been inflated. As the mixture
solidifies over a period of time, the pressure in the inflated chamber is
retained,
thereby maintaining the seal load on the wellbore.
[0051] When the filler is a bentonite/polyacrylamide mixture, water is used as
the
reactant fluid. When mixed with water downhole, a clay is formed, and the
water
soluble polymer flocculates and congeals the clay to form a much stronger and
stiffer cement-like plug. Various filler materials, such as those disclosed in
U.S.
Patent Nos. 4,633,950; 4,503,170; 4,475,594; 4,445,576; 4,442,241; and
4,391,925, are also suitable for use without deviating from the aspects of the
present invention.
[0052] It has been observed that the seal load may change over time. This loss
of
seal load may be offset in several ways. First, a sealing element made of a
swelling elastomer or natural rubber tends to expand as it adsorbs
hydrocarbons or
other fluids over a period of time. This further expansion of the sealing
element
enhances the seal load on the wellbore over time. Second, in situations where
the
sealing member is set in an unstable formation, such as an unstable formation
tending to collapse inwardly over time, the re-stressed formation exert a
force
against the sealing element to offset the loss of seal load, thereby retaining
the seal
load on the formation. Third, the sealing member may be inflated to a pressure
above the pore pressure of the formation. This over-pressurization maintains
an
effective seal load over time. Fourth, the relatively high temperatures
experienced
downhole tend to cause the sealing member to swell.
[0053] In another aspect, the seal assembly 50 may be located in the wellbore
in a
manner as to avoid or minimize restriction of the wellbore. The assembly 50
may
be self-hanging by expanding the sealing members 100 into contact with the
wellbore. Alternatively, an expandable anchor may be used to locate and hang
the
assembly 50 in the wellbore.
[0054] In another aspect, the seal assembly 750 may be arranged and
constructed
to isolate more than one zone. Figure 12 is a schematic view of a seal
14
CA 02467903 2004-05-20
assembly 750 designed to isolate a plurality of producing and non-producing
zones
701, 702, respectively. The seal assembly 750 may include a first and second
sealing members 700A, 700B positioned to isolate the producing zone 701. An
expandable sand screen 720 connecting the sealing members 700A, 700B allows
the recovery of hydrocarbons from the producing zone 701. The seal assembly
750 may further include expandable solid tubulars 730 positioned along non-
producing zones 702. As shown, a solid tubular 730 cooperate with the second
and third sealing members 700B, 700C to isolate the non-producing zone 702.
Furthermore, migration of fluids from the non-producing zone 702 along the
wellbore annulus to the producing zone 701 is prevented. In this manner,
aspects
of the present invention provide a seal assembly 750 for managing multiple
zones.
[0055] In another aspect, the ports, apertures, and channels in the sealing
members may be of any suitable shape other than circular. For example, part of
the mandrel may be slotted or otherwise perforated and on expansion may form
diamond or other shaped openings.
[0056] While the foregoing is directed to embodiments of the present
invention,
other and further embodiments of the invention may be devised without
departing
from the basic scope thereof, and the scope thereof is determined by the
claims
that follow.
